Thermoelectric heat exchange system comprising cascaded cold side heat sinks

ABSTRACT

A thermoelectric refrigeration system including at least one cooling chamber and a thermoelectric heat exchange system. The thermoelectric heat exchange system includes cascaded heat sinks. The cascaded heat sinks include cascaded cold side heat sinks and a hot side heat sink. The cascaded cold side heat sinks include a first cold side heat sink and a second cold side heat sink. The thermoelectric heat exchange system also includes a first plurality of thermoelectric coolers disposed between the first cold side heat sink and the second cold side heat sink and a second plurality of thermoelectric coolers disposed between the second cold side heat sink and the hot side heat sink. Each thermoelectric cooler is a module including multiple thermoelectric devices.

RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.13/836,525 entitled THERMOELECTRIC REFRIGERATION SYSTEM CONTROL SCHEMEFOR HIGH EFFICIENCY PERFORMANCE, filed Mar. 15, 2013, the disclosure ofwhich is hereby incorporated herein by reference in its entirety. Thisapplication also claims the benefit of:

-   -   Provisional Application Ser. No. 61/643,622, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,625, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,628, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,631, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,635, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,640, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,644, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,646, filed May 7, 2012;    -   Provisional Application Ser. No. 61/643,649, filed May 7, 2012;    -   Provisional Application Ser. No. 61/716,882, filed Oct. 22,        2012;    -   Provisional Application Ser. No. 61/716,885, filed Oct. 22,        2012; and    -   Provisional Application Ser. No. 61/739,239, filed Dec. 19,        2012;        the disclosures of which are hereby incorporated herein by        reference in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to a thermoelectric refrigeration systemand more particularly relates to controlling thermoelectric devices toefficiently maintain a desired set point temperature in a thermoelectricrefrigeration system.

BACKGROUND

Today, many refrigeration systems are vapor compression based andutilize a thermostatically regulated duty cycle control. However,typical vapor compression based refrigeration systems are not dynamicenough to meet both the steady state and transient demand, such asduring pull down or recovery. Thus, vapor compression basedrefrigeration systems tend to have excess cooling capabilities that farexceed heat extraction demands required during steady state operation.While the extra capacity provided by the excess cooling capabilitiesallows improved pull down performance, large current surges prevalentduring start-up requires higher capacity and consequently more expensivecomponents to handle the loads. Moreover, the large current surges andloads incurred by duty cycle control excessively wear the components,thereby potentially causing premature failure. Further, by the verynature of their control, thermodynamic limits, and product performancedemands, vapor compression based refrigeration systems are lessefficient than optimum.

The sub-optimum efficiency disadvantage of vapor compression basedrefrigeration systems relates to precisely controlling the temperaturewithin a cooling chamber. Typically, when a temperature within a coolingchamber exceeds a certain value, the vapor compression basedrefrigeration system activates and continues to run until thetemperature in the cooling chamber is below the certain value. Once thecooling chamber reaches a temperature below the certain value, the vaporcompression based refrigeration system shuts off. Nonetheless, inaddition to excessive wear as noted above, this type of control schemewill typically have a relatively large control band and a relativelylarge internal temperature stratification in an effort to minimizeenergy consumption and allow for operation in varied ambient conditions.This regime is most often utilized because throttling or capacityvariation is difficult and expensive to implement into the vaporcompression cycle and provides limited efficacy as volumetric efficiencyfalls.

Accordingly, what is needed is a system and method for preciselycontrolling the temperature within a cooling chamber where theefficiency of the components used to extract heat from the coolingchamber is maximized. Furthermore, what is needed is a system and methodthat allow for individually selecting components, and thereby capacity,within a refrigeration system based on the cooling demands of a coolingchamber.

SUMMARY

Embodiments of the present disclosure relate to controlling multipleThermoelectric Coolers (TECs) to maintain a set point temperature of achamber. In one embodiment, a controller receives temperature datacorresponding to a temperature of the chamber. Based on the temperaturedata, the controller selectively controls two or more subsets of theTECs to maintain the temperature of the chamber at a desired set pointtemperature. Each subset includes one or more different TECs. In oneembodiment, the controller selectively controls the two or more subsetsof the TECs by, for each subset of the TECs, independently activating ordeactivating the subset of the TECs, independently controlling a currentsupplied to the subset of the TECs, and/or independently controlling aduty cycle of the subset of the TECs. In this manner, the controller isenabled to control the TECs such that the TECs operate to efficientlymaintain the temperature of the chamber at the set point temperature.

In another embodiment, a thermoelectric refrigeration system includesone or more subsets of TECs and a controller configured to selectivelycontrol the one or more subsets of TECs. In order to selectively controlthe one or more subsets of TECs, the controller is configured to selectone or more control schemes based on temperature data and a desiredperformance profile and control the one or more subsets of TECsaccording to the one or more control schemes. The one or more controlschemes are selected by the controller from a set of control schemes ofthe controller, where the set of control schemes of the controllerincludes two or more of a group consisting of: independently controllingan activation and deactivation of each subset of TECs in the one or moresubsets of TECs, independently controlling a current provided to eachsubset of TECs in the one or more subset of TECs, and independentlycontrolling a duty cycle of each subset of TECs in the one or moresubsets of TECs. Each subset of TECs includes one or more differentTECs.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates a thermoelectric refrigeration system having acooling chamber, a heat exchanger including a cartridge that includesmultiple Thermoelectric Coolers (TECs) disposed between a cold side heatsink and a hot side heat sink, and a controller that controls the TECsto maintain a set point temperature within the cooling chamber inaccordance with one embodiment of the present disclosure;

FIG. 2 is a graph that illustrates a cooling capacity and coolingefficiency of a TEC to an input current of the TEC;

FIG. 3 is a more detailed illustration of the cartridge of FIG. 1 inwhich the cartridge includes the TECs disposed on an interconnect boardthat enables selective control of multiple different subsets of the TECsin the array of TECs in accordance with one embodiment of the presentdisclosure;

FIG. 4 is a more detailed illustration of the cartridge of FIG. 1 inwhich the cartridge includes the TECs disposed on an interconnect boardthat enables selective control of multiple different subsets of the TECsin the array of TECs in accordance with another embodiment of thepresent disclosure;

FIG. 5 is a more detailed illustration of the cartridge of FIG. 1 inwhich the cartridge includes the TECs disposed on an interconnect boardthat enables selective control of multiple different subsets of the TECsin accordance with another embodiment of the present disclosure;

FIG. 6 is a more detailed illustration of the cartridge of FIG. 1 inwhich the cartridge includes a single TEC disposed on an interconnectboard in accordance with another embodiment of the present disclosure;

FIG. 7 is a more detailed illustration of the cartridge of FIG. 1 inwhich the cartridge includes four TECs disposed on an interconnect boardin accordance with another embodiment of the present disclosure;

FIG. 8 is a more detailed illustration of the cartridge of FIG. 1 inwhich the cartridge includes six TECs disposed on an interconnect boardin accordance with another embodiment of the present disclosure;

FIG. 9 shows the interconnect board of FIG. 3 without the TECs inaccordance with one embodiment of the present disclosure;

FIG. 10 illustrates the interconnect board of FIG. 4 without the TECs inaccordance with another embodiment of the present disclosure;

FIG. 11 shows the interconnect board of FIG. 5 without the TECs inaccordance with another embodiment of the present disclosure;

FIG. 12 illustrates the interconnect board of FIG. 6 without the TEC inaccordance with another embodiment of the present disclosure;

FIG. 13 illustrates the interconnect board of FIG. 7 without the TECs inaccordance with another embodiment of the present disclosure;

FIG. 14 shows the interconnect board of FIG. 8 without the TECsaccording to another embodiment of the present disclosure;

FIG. 15 illustrates an example of one system component layout detailingvarious operating states, inputs, and outputs of the controller of FIG.1 according to one embodiment of the present disclosure;

FIG. 16 is a more detailed illustration of the operation of thecontroller of FIG. 1 when operating in the various operating states ofFIG. 15 according to one embodiment of the present disclosure;

FIG. 17 illustrates a method of operating the controller of FIG. 1 tomaintain the temperature of the cooling chamber at a set pointtemperature in accordance with one embodiment of the present disclosure;

FIG. 18 illustrates a method of operating the controller of FIG. 1 tomaintain the temperature of the cooling chamber at a set pointtemperature in accordance with another embodiment of the presentdisclosure;

FIG. 19 illustrates a method of operating the controller of FIG. 1 tomonitor a temperature of one or more components of the heat exchanger ofFIG. 1 to detect an over-temperature condition and, in response, takeaction to lower the temperature of the one or more components of theheat exchanger in accordance with one embodiment of the presentdisclosure;

FIGS. 20A through 20C illustrate a thermoelectric refrigeration systemhaving multiple parallel heat exchangers in accordance with anotherembodiment of the present disclosure;

FIG. 21 illustrates a thermoelectric refrigeration system that includestwo cooling chambers each having separate, thermally-coupled heat sinksin accordance with another embodiment of the present disclosure;

FIG. 22 is a more detailed illustration of the heat exchanger of FIG. 1in accordance with one embodiment of the present disclosure;

FIGS. 23 and 24 graphically illustrate a thermal diode effect of theaccept loop and the reject loop coupled to the heat exchanger of FIG. 22according to one embodiment of the present disclosure;

FIG. 25 illustrates a thermal diode effect of a hybrid heat exchanger inaccordance with one embodiment of the present disclosure;

FIGS. 26 through 29 are schematics illustrating a configuration of acold side heat sink of the heat exchangers of FIGS. 1 and 21 inaccordance with one embodiment of the present disclosure;

FIG. 30 illustrates a heat exchanger having physically separated hotside and cold side heat sinks that are thermally coupled via a heatconduit according to one embodiment of the present disclosure;

FIG. 31 is a schematic illustrating heat flow in the heat exchanger ofFIG. 30 according to one embodiment of the present disclosure;

FIGS. 32 and 33 illustrate embodiments of a thermoelectric refrigerationsystem that utilizes the heat exchanger of FIG. 30; and

FIG. 34 is a block diagram for the controller of FIG. 1 in accordancewith one embodiment of the present disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer, or region to another element, layer, or region asillustrated in the Figures. It will be understood that these terms andthose discussed above are intended to encompass different orientationsof the device in addition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

FIG. 1 illustrates a thermoelectric refrigeration system 100 accordingto one embodiment of the present disclosure. As illustrated, thethermoelectric refrigeration system 100 includes a cooling chamber 102,a heat exchanger 104, and a controller 106 that controls cooling withinthe cooling chamber 102. The heat exchanger 104 includes a hot side heatsink 108, a cold side heat sink 110, and a cartridge 112 includingmultiple Thermoelectric Coolers (TECs), where each TEC has a cold sidethat is thermally coupled with the cold side heat sink 110 and a hotside that that is thermally coupled with the hot side heat sink 108. TheTECs are preferably thin film devices. When one or more of the TECs areactivated by the controller 106, the activated TEC(s) operates to heatthe hot side heat sink 108 and cool the cold side heat sink 110 tothereby facilitate heat transfer to extract heat from the coolingchamber 102. More specifically, when one or more of the TECs areactivated, the hot side heat sink 108 is heated to thereby create anevaporator and the cold side heat sink 110 is cooled to thereby create acondenser.

Acting as a condenser, the cold side heat sink 110 facilitates heatextraction from the cooling chamber 102 via an accept loop 114 coupledwith the cold side heat sink 110. The accept loop 114 is thermallycoupled to an interior wall 115 of the thermoelectric refrigerationsystem 100. The interior wall 115 defines the cooling chamber 102. Inone embodiment, the accept loop 114 is either integrated into theinterior wall 115 or integrated directly onto the surface of theinterior wall 115. The accept loop 114 is formed by any type of plumbingthat allows for a cooling medium (e.g., a two-phase coolant) to flow orpass through the accept loop 114. Due to the thermal coupling of theaccept loop 114 and the interior wall 115, the cooling medium extractsheat from the cooling chamber 102 as the cooling medium flows throughthe accept loop 114. The accept loop 114 may be formed of, for example,copper tubing, plastic tubing, stainless steel tubing, aluminum tubing,or the like.

The condenser formed by the cold side heat sink 110 and the accept loop114 operates according to any suitable heat exchange technique. In onepreferred embodiment, the accept loop 114 operates in accordance withthermosiphon principles (i.e., acts as a thermosiphon) such that thecooling medium travels from the cold side heat sink 110 through theaccept loop 114 and back to the cold side heat sink 110 to thereby coolthe cooling chamber 102 using two-phase, passive heat transport. Inparticular, passive heat exchange occurs through natural convectionbetween the cooling medium in the accept loop 114 and the coolingchamber 102. In one embodiment, the cooling medium is in liquid formwhen the cooling medium comes into thermal contact with the coolingchamber 102. Specifically, passive heat exchange occurs between theenvironment in the cooling chamber 102 and the cooling medium within theaccept loop 114 such that the temperature in the cooling chamber 102decreases and the temperature of the cooling medium increases and/orundergoes a phase change. When the temperature of the cooling mediumincreases, the density of the cooling medium decreases, such as throughevaporation. As a result, the cooling medium moves in an upwarddirection via buoyancy forces in the accept loop 114 towards the heatexchanger 104 and specifically towards the cold side heat sink 110. Thecooling medium comes into thermal contact with the cold side heat sink110, where heat exchange occurs between the cooling medium and the coldside heat sink 110. When heat exchange occurs between the cooling mediumand the cold side heat sink 110, the cooling medium condenses and againflows through the accept loop 114 via gravity in order to extractadditional heat from the cooling chamber 102. Thus, in some embodiments,the accept loop 114 functions as an evaporator when cooling the coolingchamber 102.

As noted above, the heat exchanger 104 includes the cartridge 112disposed between the hot side heat sink 108 and the cold side heat sink110. The TECs in the cartridge 112 have hot sides (i.e., sides that arehot during operation of the TECs) that are thermally coupled with thehot side heat sink 108 and cold sides (i.e., sides that are cold duringoperation of the TECs) that are thermally coupled with the cold sideheat sink 110. The TECs within the cartridge 112 effectively facilitateheat transfer between the cold side heat sink 110 and the hot side heatsink 108. More specifically, when heat transfer occurs between thecooling medium in the accept loop 114 and the cold side heat sink 110,the active TECs transfer heat between the cold side heat sink 110 andthe hot side heat sink 108.

Acting as an evaporator, the hot side heat sink 108 facilitatesrejection of heat to an environment external to the cooling chamber 102via a reject loop 116 coupled to the hot side heat sink 108. The rejectloop 116 is thermally coupled to an outer wall 118, or outer skin, ofthe thermoelectric refrigeration system 100. The outer wall 118 is indirect thermal contact with the environment external to the coolingchamber 102. Further, the outer wall 118 is thermally isolated from theaccept loop 114 and the interior wall 115 (and thus the cooling chamber102) by, for example, appropriate insulation. In one embodiment, thereject loop 116 is integrated into the outer wall 118 or integrated ontothe surface of the outer wall 118. The reject loop 116 is formed of anytype of plumbing that allows a heat transfer medium (e.g., a two-phasecoolant) to flow or pass through the reject loop 116. Due to the thermalcoupling of the reject loop 116 and the external environment, the heattransfer medium rejects heat to the external environment as the heattransfer medium flows through the reject loop 116. The reject loop 116may be formed of, for example, copper tubing, plastic tubing, stainlesssteel tubing, aluminum tubing, or the like.

The evaporator formed by the hot side heat sink 108 and the reject loop116 operates according to any suitable heat exchange technique. In onepreferred embodiment, the reject loop 116 operates in accordance withthermosiphon principles (i.e., acts as a thermosiphon) such that theheat transfer medium travels from the hot side heat sink 108 through thereject loop 116 and back to the hot side heat sink 108 to thereby rejectheat using two-phase, passive heat transport. In particular, the hotside heat sink 108 transfers the heat received from the cold side heatsink 110 to the heat transfer medium within the reject loop 116. Onceheat is transferred to the heat transfer medium, the heat transfermedium changes phase and travels through the reject loop 116 and comesinto thermal contact with the outer wall 118 such that heat is expelledto the environment external to the cooling chamber 102. When the heattransfer medium within the reject loop 116 is in direct thermal contactwith the outer wall 118, passive heat exchange occurs between the heattransfer medium in the reject loop 116 and the external environment. Asis well known, the passive heat exchange causes condensation of the heattransfer medium within the reject loop 116, such that the heat transfermedium travels back to the heat exchanger 104 by force of gravity. Thus,the reject loop 116 functions as a condenser when rejecting heat to theenvironment external to the cooling chamber 102.

As discussed below in detail, in one preferred embodiment, the heatexchanger 104 is not in direct thermal contact with the cooling chamber102 and is instead thermally isolated from the cooling chamber 102.Likewise, the heat exchanger 104 is not in direct thermal contact withthe outer wall 118 and is instead thermally isolated from the outer wall118. Accordingly, as will be detailed below, the heat exchanger 104 isthermally isolated from both the cooling chamber 102 and the outer wall118 of the thermoelectric refrigeration system 100. Importantly, thisprovides a thermal diode effect by which heat is prevented from leakingback into the cooling chamber 102 when the TECs are deactivated.

The controller 106 operates to control the TECs within the cartridge 112in order to maintain a desired set point temperature within the coolingchamber 102. In general, the controller 106 operates to selectivelyactivate/deactivate the TECs, selectively control an input current ofthe TECs, and/or selectively control a duty cycle of the TECs tomaintain the desired set point temperature. Further, in preferredembodiments, the controller 106 is enabled to separately, orindependently, control one or more and, in some embodiments, two or moresubsets of the TECs, where each subset includes one or more differentTECs. Thus, as an example, if there are four TECs in the cartridge 112,the controller 106 may be enabled to separately control a firstindividual TEC, a second individual TEC, and a group of two TECs (i.e.,a first and a second individual TEC and a group of two TECs). By thismethod, the controller 106 can, for example, selectively activate one,two, three, or four TECs independently, at maximized efficiency, asdemand dictates.

Continuing this example, the controller 106 may be enabled to separatelyand selectively control: (1) activation/deactivation of the firstindividual TEC, an input current of the first individual TEC, and/or aduty cycle of the first individual TEC; (2) activation/deactivation ofthe second individual TEC, an input current of the second individualTEC, and/or a duty cycle of the second individual TEC; and (3)activation/deactivation of the group of two TECs, an input current ofthe group of two TECs, and/or a duty cycle of the group of two TECs.Using this separate selective control of the different subsets of theTECs, the controller 106 preferably controls the TECs to enhance anefficiency of the thermoelectric refrigeration system 100. For example,the controller 106 may control the TECs to maximize efficiency whenoperating in a steady state mode, such as when the cooling chamber 102is at the set point temperature or within a predefined steady statetemperature range. However, during pull down or recovery, the controller106 may control the TECs to achieve a desired performance such as, forexample, maximizing heat extraction from the cooling chamber 102,providing a tradeoff between pull down/recovery times and efficiency, orthe like.

Before proceeding, a brief discussion of a cooling capacity versus aninput current characteristic and efficiency versus an input currentcharacteristic of a TEC is beneficial. In this regard, FIG. 2 is a graphthat illustrates cooling capacity (Q) and cooling efficiency (COP) of aTEC versus an input current of a TEC. The cooling efficiency is morespecifically represented by a Coefficient of Performance (COP). Asillustrated in FIG. 2, as the input current (I) of the TEC increases,the cooling capacity of the TEC also increases. The point on the coolingcapacity (Q) curve that represents where a maximum amount of heat isbeing removed by the TEC is denoted as Q_(max). Thus, when the TEC isoperating at Q_(max), the TEC is removing the greatest amount of heatpossible. The TEC operates at Q_(max) when a corresponding maximumcurrent I_(max) is provided to the TEC. FIG. 2 also illustrates the COPof the TEC as a function of current. For cooling applications, the COPof a TEC is a ratio of heat removed over an amount of work input to theTEC to remove the heat. The amount of heat, or capacity, (Q) at whichthe COP of the TEC is maximized is denoted as Q_(COPmax). The TECoperates at Q_(COPmax) when a current I_(COPmax) is provided to the TEC.Thus, the efficiency, or COP, of the TEC is maximized when the currentI_(COPmax) is provided to the TEC such that the TEC operates atQ_(COPmax).

As discussed below in detail, in preferred embodiments, the controller106 controls the TECs within the cartridge 112 such that, during steadystate operation, one or more of the TECs are activated and operated atQ_(COPmax) and the remaining TECs are deactivated to thereby maximizeefficiency. The number of TECs activated, and conversely the number ofTECs deactivated, is dictated by demand. Conversely, during pull down orrecovery, one or more and possibly all of the TECs within the cartridge112 are activated and operated according to a desired performanceprofile. One example of the desired performance profile is that all ofthe TECs are activated and operated at Q_(max) in order to minimize pulldown or recovery time. However, the desired performance profile mayalternatively provide a tradeoff between pull down or recovery time andefficiency where, for example, all of the TECs are activated and areoperated at a point between Q_(COPmax) and Q_(max). Note that, asdiscussed below, control of the TECs is not limited to these examples.

As noted above, FIG. 2 illustrates the cooling capacity and coolingefficiency of a single TEC. Increasing the number of TECs linearlyincreases the heat removal capacity without affecting the operating COPof the thermoelectric refrigeration system 100 employing the TECs. Thus,if the thermoelectric refrigeration system 100 includes four TECs, thenthe heat removal capacity of the thermoelectric refrigeration system 100is increased fourfold in comparison to an embodiment of thethermoelectric refrigeration system 100 that includes a single TEC whileallowing the entire system to, in some preferred embodiments, operatebetween off, Q_(COPmax), and Q_(max).

It should be noted that while the application of electrical current to aTEC and FIG. 2 are discussed in the context of cooling, the sameprinciples apply in the context of heat recovery/power generation, wherethe TECs are used to generate power, or current, in response to heat.

TEC Cartridge

Before discussing the details of the operation of the controller 106 toseparately and selectively control the TECs, it is beneficial to discussembodiments of the cartridge 112 of FIG. 1 that enable separate andselective control of the TECs. Note that while the following discussionof the cartridge 112 is with respect to the thermoelectric refrigerationsystem 100 of FIG. 1, the cartridge 112 is not limited to use in thethermoelectric refrigeration system 100 of FIG. 1 nor thermoelectricrefrigeration in general. For instance, the cartridge 112 may beutilized in heat recovery or power generation applications.

As noted above, the TECs in the cartridge 112 are used to regulate thetemperature of the cooling chamber 102. In order to meet desired coolingcapacity for many refrigeration applications, the thermoelectricrefrigeration system 100 utilizes multiple TECs. The use of multipleTECs is beneficial over the use of a single large TEC because themultiple TECs can be separately controlled to provide the desiredperformance under varying conditions. In contrast, a single over-sizedTEC that is designed to provide a maximum desired capacity for pull downor recovery does not provide this flexibility. For example, duringsteady state conditions, the single over-sized TEC would typicallyoperate at a low capacity point that corresponds to a low COP value. Inother words, the over-sized TEC would operate inefficiently. Incontrast, the controller 106 is enabled to separately control subsets ofthe TECs in the cartridge 112 in order to maximize efficiency duringsteady state conditions.

FIGS. 3 through 5 illustrate embodiments of the cartridge 112 thatenable the controller 106 to separately and selectively controldifferent subsets of the TECs according to a desired control scheme.Note, however, that the embodiments of FIGS. 3 through 5 are onlyexamples. The cartridge 112 may be configured to hold any number of TECsand to allow any number of subsets of the TECs to be separatelycontrolled. Each subset generally includes one or more TECs. Further,the different subsets may include the same number or different numbersof TECs.

In the embodiment of FIG. 3, the cartridge 112 includes TECs 120 athrough 120 f (more generally referred to herein collectively as TECs120 and individually as TEC 120) disposed on an interconnect board 122.The TECs 120 are thin film devices. Some non-limiting examples of thinfilm TECs are disclosed in U.S. Pat. No. 8,216,871, entitled METHOD FORTHIN FILM THERMOELECTRIC MODULE FABRICATION, which is herebyincorporated herein by reference in its entirety. The interconnect board122 includes electrically conductive traces 124 a through 124 d (moregenerally referred to herein collectively as traces 124 and individuallyas trace 124) that define four subsets of the TECs 120 a through 120 f.In particular, the TECs 120 a and 120 b are electrically connected inseries with one another via the trace 124 a and, as such, form a firstsubset of the TECs 120. Likewise, the TECs 120 c and 120 d areelectrically connected in series with one another via the trace 124 band, as such, form a second subset of the TECs 120. The TEC 120 e isconnected to the trace 124 d and, as such, forms a third subset of theTECs 120, and the TEC 120 f is connected to the trace 124 c and, assuch, forms a fourth subset of the TECs 120. The controller 106 (FIG. 1)can, in no particular order, selectively control the first subset ofTECs 120 (i.e., the TECs 120 a and 120 b) by controlling a currentapplied to the trace 124 a, selectively control the second subset of theTECs 120 (i.e., the TECs 120 c and 120 d) by controlling a currentapplied to the trace 124 b, selectively control the third subset of theTECs 120 (i.e., the TEC 120 e) by controlling a current applied to thetrace 124 d, and selectively control the fourth subset of the TECs 120(i.e., the TEC 120 f) by controlling a current applied to the trace 124c. Thus, using the TECs 120 a and 120 b as an example, the controller106 can selectively activate/deactivate the TECs 120 a and 120 b byeither removing current from the trace 124 a (deactivate) or by applyinga current to the trace 124 a (activate), selectively increase ordecrease the current applied to the trace 124 a while the TECs 120 a and120 b are activated, and/or control the current applied to the trace 124a in such a manner as to control a duty cycle of the TECs 120 a and 120b while the TECs 120 a and 120 b are activated (e.g., Pulse WidthModulation of the current).

The interconnect board 122 includes openings 126 a and 126 b (moregenerally referred to herein collectively as openings 126 andindividually as opening 126) that expose bottom surfaces of the TECs 120a through 120 f. When disposed between the hot side heat sink 108(FIG. 1) and the cold side heat sink 110 (FIG. 1), the openings 126 aand 126 b enable the bottom surfaces of the TECs 120 a through 120 f tobe thermally coupled to the appropriate heat sink 108 or 110.

In accordance with embodiments of the present disclosure, duringoperation, the controller 106 can selectively activate or deactivate anycombination of the subsets of the TECs 120 by applying or removingcurrent from the corresponding traces 124 a through 124 d. Further, thecontroller 106 can control the operating points of the active TECs 120by controlling the amount of current provided to the correspondingtraces 124 a through 124 d. For example, if only the first subset of theTECs 120 is to be activated and operated at Q_(COPmax) during steadystate operation, then the controller 106 provides the current I_(COPmax)to the trace 124 a to thereby activate the TECs 120 a and 120 b andoperate the TECs 120 a and 120 b at Q_(COPmax) and removes current fromthe other traces 124 b through 124 d to thereby deactivate the otherTECs 120 c through 120 f.

In the embodiment shown with reference to FIG. 3, the cartridge 112includes the TECs 120 a through 120 f. In accordance with embodiments ofthe present disclosure, the cartridge 112 may include any number of TECs120. For example, in the embodiment shown with reference to FIG. 4, thecartridge 112 includes the interconnect board 122 having only two TECs120, the TECs 120 e and 120 f. In this embodiment, the controller 106(FIG. 1) can individually control the TECs 120 e and 120 f bycontrolling the currents provided to the corresponding traces 124 d and124 c, respectively. As another example, the cartridge 112 can includeonly four TECs 120, such as the TECs 120 c through 120 f, as shown withreference to FIG. 5. In this embodiment, the interconnect board 122includes the traces 124 b through 124 d, which provide current to theTECs 120 c through 120 f, respectively. Moreover, the correspondingsubsets of the TECs 120 can be controlled by the controller 106 byproviding the appropriate currents to the traces 124 b through 124 d.

While FIGS. 3 through 5 illustrate embodiments of the cartridge 112 thatenable selective control of different TECs on the cartridge 112, FIGS. 6through 8 illustrate embodiments of the cartridge 112 that may beutilized if selective control is not needed. In these embodiments, theinput current of the TECs and/or a duty cycle of the TECs may be variedto provide a desired capacity, a desired efficiency, or some tradeoffbetween capacity and efficiency. In particular, FIG. 6 illustrates anembodiment of the cartridge 112 that includes an interconnect board 128and a single TEC 130 disposed on the interconnect board 128. An opening131 in the interconnect board 128 exposes a bottom surface of the TEC130. The controller 106 (FIG. 1) can control the capacity and efficiencyof the TEC 130 by controlling a current input to the TEC 130 via anelectrically conductive trace 132 on the interconnect board 128.

FIG. 7 illustrates an embodiment of the cartridge 112 that is similar tothat of FIG. 6 but where the cartridge 112 includes four TECs. Morespecifically, the cartridge 112 includes an interconnect board 134 andfour TECs 136 disposed on the interconnect board 134. There are openings137 in the interconnect board 134 to expose bottom surfaces of the TECs136. Again, the controller 112 can control a capacity and efficiency ofthe TECs 136 by controlling a current input to the TECs 136 and/or aduty cycle of the TECs 136 via an electrically conductive trace 138 onthe interconnect board 134.

FIG. 8 illustrates yet another example of the cartridge 112 that issimilar to that of FIGS. 6 and 7 but where the cartridge 112 includessix TECs. More specifically, the cartridge 112 includes an interconnectboard 140 and six TECs 142 disposed on the interconnect board 140. Thereare openings 143 in the interconnect board 140 to expose bottom surfacesof the TECs 142. Again, the controller 112 can control a capacity andefficiency of the TECs 142 by controlling a current input to the TECs142 and/or a duty cycle of the TECs 142 via an electrically conductivetrace 144 on the interconnect board 140. Note that the embodiments ofFIGS. 6 through 8 are only examples. The cartridge 112 may be configuredto include any number of TECs or conductive traces in series or parallelconfiguration.

FIGS. 9 through 14 illustrate the interconnect boards 122, 128, 134, and140 of FIGS. 3 through 8, respectively, but without TECs attached to theinterconnect boards. FIGS. 9 through 14 more clearly illustrate theopenings 126, 131, 137, and 143 in the interconnect boards that exposethe bottom surfaces of the TECs or, in other words, enable thermalcoupling between the bottom surfaces of the TECs and the appropriateheat sink 108 or 110. FIGS. 9 through 14 also illustrate contacts 146,148, 150, and 152 that enable electrical and mechanical connectionbetween the interconnect boards 122, 128, 134, and 140 and correspondingTECs.

Selectively Controlling the TECs

The following is a detailed discussion of embodiments of the operationof the controller 106 of FIG. 1. For this discussion, it is assumed thatthe cartridge 112 is the cartridge 112 of FIG. 3, which enablesselective control of multiple different subsets of the TECs 120. Note,however, that the use of the cartridge 112 of FIG. 3 is only an example.

FIG. 15 illustrates the operation of the controller 106 according to oneembodiment of the present disclosure. As illustrated, the controller 106receives temperature data from temperature inputs 154 and 156. Thetemperature inputs 154 and 156 can be any type of temperature sensors.The temperature data includes a temperature (T_(CH)) of the coolingchamber 102 and a temperature (T_(R)) on the reject side, or hot side,of the heat exchanger 104. The reject side of the heat exchanger 104 isthe hot side of the heat exchanger 104. Thus, for example, thetemperature (T_(R)) may be a temperature of the hot side heat sink 108.Based on the temperature data, the controller 106 determines a currentmode of operation of the thermoelectric refrigeration system 100. Inthis embodiment, the current mode of operation is one of a pull downmode 158, a steady state mode 160, an over temperature mode 162, and arecovery mode 163. The pull down mode 158 generally occurs when thethermoelectric refrigeration system 100 is first powered on. The steadystate mode 160 occurs when the temperature of the cooling chamber 102 isat or near the desired set point temperature. In particular, thetemperature of the cooling chamber 102 is at or near the desired setpoint temperature when the temperature of the cooling chamber 102 iswithin a predefined steady state range that includes the set pointtemperature (e.g., the set point temperature of the cooling chamber102±2 degrees). The over temperature mode 162 is when the temperature onthe reject side of the heat exchanger 104 is above a predefined maximumallowable temperature. The over temperature mode 162 is a safety modeduring which the temperature of the reject side of the heat exchanger104, and thus the hot side temperature of the TECs 120, is reduced inorder to protect the TECs 120 from damage. Lastly, the recovery mode 163is when the temperature of the cooling chamber 102 increases outside ofthe steady state range due to, for example, heat leak into the coolingchamber 102, opening of the door of the cooling chamber 102, or thelike.

The operation of the controller 106 in the different modes 158, 160,162, and 163 in one embodiment of the present disclosure is illustratedin FIG. 16. As illustrated in FIG. 16, when operating in the pull downmode 158, the controller 106 controls the currents to all of the TECs120 such that all of the TECs 120 operate at a power level betweenQ_(COPmax) and Q_(max) as the desired performance profile dictates. Inother words, the controller 106 causes a current between I_(COPmax) andI_(max) to be provided to all of the TECs 120. The controller 106determines when the thermoelectric refrigeration system 100 is in thepull down mode 158 based on, for example, being initially powered on,such as when the thermoelectric refrigeration system 100 is firstpurchased or after the thermoelectric refrigeration system 100 ispowered on after becoming disconnected from a power source. Thecontroller 106 maintains all of the TECs 120 at a power level betweenQ_(COPmax) and Q_(max) until the temperature of the cooling chamber 102is pulled down to the set point temperature or within an acceptablerange of the set point temperature, as shown with reference to 164. Oncethe cooling chamber 102 is pulled down to the set point temperature, thecontroller 106 controls the operation of the TECs 120 such that all ofthe TECs 120 operate at Q_(COPmax) by causing the current I_(COPmax) tobe provided to all of the TECs 120. Moreover, the controller 106 mayreduce the number of TECs 120 that are activated once the coolingchamber 102 is pulled down to the set point temperature.

As noted above, based on the temperature data, the controller 106 alsodetermines when the thermoelectric refrigeration system 100 is in thesteady state mode 160. The thermoelectric refrigeration system 100 is inthe steady state mode 160 if the temperature of the cooling chamber 102is equal to the set point temperature or within a predetermined range ofthe set point temperature. When in the steady state mode 160, thecontroller 106 sets the required number of the TECs 120 to Q_(COPmax) asrequired by demand. In this example, all of the TECs 120 are operated atQ_(COPmax) in the steady state mode 160. During the steady state mode160, if Q_(COPmax)>Q_(leak) as shown with reference to 166, thetemperature of the cooling chamber 102 will continue to decrease. Inthis case, the controller 106 reduces the duty cycle of the activatedTECs 120 as shown with reference to 168. Conversely, ifQ_(COPmax)<Q_(leak) as shown with reference to 170, the temperature ofthe cooling chamber 102 will increase. In this case, the controller 106increases the number of active TECs 120 as available and then thecurrent provided to the active TECs 120 to a value between I_(COPmax)and I_(max) as shown with reference to 172. Notably, Q_(leak) refers tothe amount of heat leaking into the cooling chamber 102, such as heatpassing through a seal of a door of the cooling chamber 102, naturalheat conduction through the cooling chamber 102, or the like.

As mentioned above, the controller 106 also determines if the coolingchamber 102 is in the over temperature mode 162 based on the temperaturedata from the temperature input 156. During operation of thethermoelectric refrigeration system 100, the temperature at the rejectside of the heat exchanger 104 is monitored to ensure that thetemperature at the reject side of the heat exchanger 104 does not exceedthe predetermined maximum allowable temperature. The temperature of thereject side of the heat exchanger 104 may exceed the predeterminedmaximum allowable temperature when, for example, the cooling chamber 102does not cool down, such as if the door to the cooling chamber 102 isnot properly closed, or the like.

If the controller 106 determines that the temperature at the reject sideof the heat exchanger 104 exceeds the predetermined maximum allowabletemperature, in an operation 174, the controller 106 decreases thetemperature at the reject side of the heat exchanger 104 by deactivatingsome or all of the TECs 120 that are facilitating cooling or by reducingthe current being provided to the TECs 120. For example, if all of theTECs 120 are operating, either at Q_(COPmax) or Q_(max), the controller106 may deactivate one or more of the TECs 120 or preferably all of theTECs 120. In another example, if the TECs 120 a, 120 b, 120 e, and 120 fare operating at Q_(max), the controller 106 may deactivate the TECs 120e and 120 f such that only the TECs 120 a and 120 b are operating atQ_(max) and facilitating heat extraction from the cooling chamber 102.In another example, if the TECs 120 a through 120 d are operating atQ_(COPmax), the controller 106 may deactivate the TECs 120 c and 120 dand then also activate the TEC 120 e in order to maintain thetemperature of the cooling chamber 102 as close as to the set pointtemperature as possible without harming the cartridge 112. It should benoted that the controller 106 may deactivate any number of active TECs120 and activate any number of the inactive TECs 120 in response todetermining that the temperature of the heat exchanger 104 exceeds themaximum allowable temperature.

As noted above, if the controller 106 determines that the temperature ofthe heat exchanger 104 exceeds the predetermined maximum allowabletemperature, the controller 106 may reduce the current being provided tothe TECs 120 in addition to or as an alternative to deactivating some orall of the TECs 120. To further illustrate this functionality, if all ofthe TECs 120 are operating, either at Q_(COPmax) or Q_(max), thecontroller 106 may decrease the amount of current being provided to eachof the TECs 120. For example, if all of the TECs 120 are operating atQ_(max), the controller 106 may reduce the current from I_(max) to avalue that is between I_(COPmax) and I_(max). In addition, if all of theTECs 120 are operating at Q_(COPmax) or Q_(max), the controller 106 mayonly reduce the current provided to some of the TECs 120 in order toreduce the temperature of the heat exchanger 104. In a furtherembodiment, the controller 106 may also deactivate some of the TECs 120and simultaneously decrease the current to some or all of the TECs 120that are still activated if the temperature of the heat exchanger 104exceeds the predetermined maximum allowable temperature.

When in the recovery mode 163, the controller 106 switches the activeTECs 120 from operating at Q_(COPmax) to operating at Q_(max) as shownat operation 175. The recovery mode 163 occurs when, during steady stateoperation, the controller 106 receives temperature data from thetemperature input 154 indicating that the temperature within the coolingchamber 102 has significantly increased above the set point temperaturewithin a short period of time. Specifically, the thermoelectricrefrigeration system 100 may enter the recovery mode 163 when thetemperature within the cooling chamber 102 increases above an upperthreshold of the steady state range of temperatures (e.g., increasesabove the set point temperature plus some predefined value that definesthe upper threshold of the desired steady state range).

It should be noted that the controls 164, 166, 168, 170, 172, 174, and175 illustrated in FIG. 16 for the different modes 158, 160, 162, and163 are only examples. The manner in which the controller 106 controlsthe TECs 120 in each of the modes 158, 160, 162, and 163 may varydepending on the particular implementation. In general, as discussedabove, the controller 106 controls the TECs 120 to reduce thetemperature of the cooling chamber 102 when in either the pull down mode158 or the recovery mode 163. The exact manner in which this is done mayvary. For example, if the performance profile is that a minimum pulldown or recovery time is desired, the controller 106 can activate all ofthe TECs 120 at Q_(max) with a 100% duty cycle (always on). Conversely,if a trade-off between pull down or recovery time and efficiency isdesired, the controller 106 can, for example, activate all of the TECs120 at Q_(COPmax) with a 100% duty cycle (always on) or at anywhere inbetween Q_(COPmax) and Q_(max). When in the steady state mode 160, thecontroller 106 generally operates to maintain the set point temperaturein an efficient manner. For example, the controller 106 can operate therequired number of the TECs 120 (e.g., all of the TECs 120 or less thanall of the TECs 120) at Q_(COPmax) based on load. This predeterminednumber of the TECs 120 is a number of the TECs 120 that is required tomaintain the set point temperature by operating at or near Q_(COPmax).If not all of the TECs 120 are needed during the steady state mode 160,then the unneeded TECs 120 are deactivated. The controller 106 can finetune the operation of the activated TECs 120 to precisely maintain theset point temperature by, for example, slightly increasing or decreasingthe input current of the activated TECs 120 such that the activated TECs120 operate slightly above Q_(COPmax) or by increasing or decreasing theduty cycle of the activated TECs 120 to compensate for Q_(leak).

Returning to FIG. 15, the thermoelectric refrigeration system 100 alsoincludes a user interface (UI) 176, a power source 178, an accessory(acc) 180, and power electronics 182. The user interface 176 allows auser to input various control parameters associated with thethermoelectric refrigeration system 100. These control parametersinclude the set point temperature of the cooling chamber 102. In someembodiments, the control parameters may additionally include values forthe steady state range of temperatures. Note that, in some embodiments,the user interface 176 may additionally allow the user or a manufacturerof the thermoelectric refrigeration system 100 to define the maximumallowable temperature for the reject side of the heat exchanger 104, thecurrent values associated with I_(COPmax) and I_(max), and/or the like.However, it should be noted that some or all of the control parametersmay be programmed or hard-coded into the controller 106.

The power source 178 provides power to the controller 106, the accessory180, and the power electronics 182. The accessory 180 may be a chamberlight or a communication module for expanded capabilities. In anembodiment where the accessory 180 is a communication module, theaccessory 180 may communicate with remote devices, such as, but notlimited to: a cellular telephone, a remotely located computing device,or even other appliances and thermoelectric refrigeration systems. In anembodiment where the accessory 180 communicates with a cellulartelephone or a remotely located computing device, the accessory 180 canprovide operational parameters (e.g., the temperature data) of thethermoelectric refrigeration system 100 and the cooling chamber 102 to aremote device or entity. In an embodiment where the accessory 180communicates with other thermoelectric refrigeration systems, theaccessory 180 may communicate operational parameters of thethermoelectric refrigeration system 100 to the other thermoelectricrefrigeration systems, such as the set point temperature, upper andlower thresholds of the set point temperature, a maximum allowabletemperature of the cooling chamber 102, the maximum allowabletemperature of the reject side of the heat exchanger 104, or the like.

The power electronics 182 generally operate to provide current to theTECs 120 in response to control inputs from the controller 106. Morespecifically, the power electronics 182 independently provide current toeach of the subsets of the TECs 120. In one embodiment, the duty cyclesof the different subsets of the TECs 120 are also controlled. In thiscase, the power electronics 182 may provide a pulse width modulationfunction by which the duty cycles of the different subsets of the TECs120 are controlled.

With reference to FIG. 17, a method of operation of the controller 106to maintain the cooling chamber 102 at the set point temperature isillustrated in accordance with one embodiment of the present disclosure.Initially, the temperature data corresponding to the temperature withinthe cooling chamber 102 and the temperature at the reject side of theheat exchanger 104 is received (step 1000). For example, a thermocouple,or any other type of temperature sensor, may be used to determine thetemperature of the cooling chamber 102 and provide the temperature astemperature data to the controller 106 in step 1000 via the temperatureinput 154. Furthermore, a thermocouple, or any other type of temperaturesensor, may be used to determine the temperature of the reject side ofthe heat exchanger 104 and provide the temperature as temperature datato the controller 106 in step 1000 via the temperature input 156.

In response to receiving the temperature data, the controller 106selectively controls the TECs based on the temperature data (step 1002).In general, the controller 106 selectively controls one or more and, insome preferred embodiments, two or more different subsets of the TECsbased on the temperature data and the set point temperature for thecooling chamber 102. Using the TECs 120 in the cartridge 112 of FIG. 3as an example, the controller 106 selectively, or separately, controlsthe different subsets of the TECs 120. More specifically, as discussedabove, the controller 106 determines whether the thermoelectricrefrigeration system 100 is in the pull down mode 158, the steady statemode 160, or the recovery mode 163 based on the temperature data and theset point temperature for the cooling chamber 102. If the controller 106determines that the thermoelectric refrigeration system 100 is in eitherthe pull down mode 158 or the recovery mode 163, the controller 106controls the TECs 120 to decrease the temperature of the cooling chamber102 by either activating TECs 120 that are currently deactivated,increasing the current provided to the activated TECs 120, and/orincreasing the duty cycle of the activated TECs 120. If the controller106 determines that the thermoelectric refrigeration system 100 is inthe steady state mode 160, the controller 106 controls the TECs 120 tomaintain the set point temperature. In the steady state mode 160, thecontroller 106 may, for example, activate or deactivate the differentsubsets of the TECs 120, increase or decrease the current provided tothe different subsets of the activated TECs 120, and/or increase ordecrease the duty cycle of the different subsets of the activated TECs120 as needed to maintain the set point temperature.

As an example, if the temperature data indicates that the thermoelectricrefrigeration system 100 is in the recovery mode 163 while the TECs 120a, 120 b, and 120 e operate at Q_(COPmax) during steady state operation,the controller 106 may activate additional subsets of the inactive TECs120 c, 120 d, and 120 f and operate the newly activated TECs 120 atQ_(COPmax). If further cooling capacity is needed, the controller 106may then increase the current provided to the active TECs 120 a, 120 b,120 c, 120 d, 120 e, and 120 f up to I_(max) in order to pull thetemperature of the cooling chamber 102 down to the set point temperatureas soon as possible. After the controller 106 selectively controls theTECs 120 to operate at Q_(max), the method returns to step 1000 and thecontroller 106 once again receives the temperature data. Returning tothe example, if the temperature data received in step 1000 indicatesthat the cooling chamber 102 has been cooled to the set pointtemperature, the controller 106 decreases the current provided to theTECs 120 a, 120 b, and 120 e from I_(max) to I_(COPmax) such that theTECs 120 a, 120 b, and 120 e operate at Q_(COPmax) for the steady statemode 160 in step 1002. In addition, the controller 106 deactivates theTECs 120 c, 120 d, and 120 f, which in this example are unused in thesteady state mode 160. The controller 106 continually repeats thisprocess to maintain the set point temperature in the cooling chamber102.

In other words, in one embodiment, the controller 106 is configured orenabled to control the TECs 120 according multiple control schemes. Thecontrol schemes include independently controlling activation anddeactivation of the different subsets of the TECs 120, independentlycontrolling a current provided to each subset of the TECs 120, and/orindependently controlling a duty cycle of each subset of the TECs 120.In operation, the controller 106 selects one or more control schemesbased on the temperature of the cooling chamber 102 and, in someembodiments, the temperature at the reject side of the heat exchanger104, as well as a desired performance profile. The desired performanceprofile may be programmable or hard-coded into the controller 106. Thedesired performance profile dictates how the TECs 120 are controlled(e.g., maximum efficiency, maximum capacity, or somewhere betweenmaximum efficiency and maximum capacity) for the different modes ofoperation. Once the control scheme(s) are selected, the controller 106controls the different subsets of the TECs 120 according to the selectedcontrol scheme(s). Thus, the controller 106 can control any combinationof activation/deactivation, current, and duty cycle for each mode ofoperation.

For example, for the steady state mode 160, the controller 106 mayselect the control scheme of activation/deactivation of the TECs 120based on the temperature of the cooling chamber 102 and a desiredperformance profile of maximizing efficiency during the steady statemode 160. In this case, the controller 106 then activates one or more ofthe subsets of TECs 120 and, in some embodiments, deactivates one ormore other subsets of the TECs 120. In addition, the controller 106 maychoose to control the current and/or duty cycle of the activated TECs120 during the steady state mode 160, in which case the controller 106independently controls the current provided to each of the activatedsubsets of TECs 120 and/or the duty cycle of each of the activatedsubsets of TECs 120. Continuing this example, for the recovery mode 163or the pull down mode 158, the controller 106 may select the controlscheme of activation/deactivation of the TECs 120 based on thetemperature of the cooling chamber 102 and a desired performance profile(e.g., minimizing pull down or recovery time). In this case, thecontroller 106 activates additional subsets of the TECs 120 notactivated during the steady state mode 160. In addition, the controller106 may choose to control the current and/or duty cycle of the activatedsubsets of TECs 120 for the pull down mode 158 or the recovery mode 163,in which case the controller 106 independently controls the current ofeach of the activated subsets of TECs 120 and/or the duty cycle of eachof the activated subsets of TECs 120.

FIG. 18 is a flow chart that illustrates a method of operation of thecontroller 106 to maintain the cooling chamber 102 at the set pointtemperature according to another embodiment of the present disclosure.Initially, the temperature data for the cooling chamber 102 and thereject side of the heat exchanger 104 is received (step 1100). After thetemperature data is received, the controller 106 determines whether thetemperature of the cooling chamber 102 is greater than an upperthreshold of the steady state range for the temperature of the coolingchamber 102 (step 1102). The steady state range is an acceptabletemperature range for the cooling chamber 102 that includes the setpoint temperature. As an example, the steady state range may be the setpoint temperature plus or minus a predefined offset (e.g., 2 degrees).If the temperature of the cooling chamber 102 is not greater than theupper threshold of the steady state range, the controller 106 determineswhether the temperature of the cooling chamber 102 is greater than alower threshold of the steady state range (step 1104).

If the temperature of the cooling chamber 102 is not greater than thelower threshold of the steady state range, the process returns to step1100. However, if the temperature of the cooling chamber 102 is belowthe lower threshold of the steady state range, the controller 106controls the TECs 120 to increase the temperature of the cooling chamber102 (step 1106). Depending on the particular embodiment, the controller106 increases the temperature of the cooling chamber 102 by deactivatingone or more of the TECs, decreasing the current input to one or more ofthe TECs 120, and/or decreasing the duty cycle of one or more of theTECs 120. Since the controller 106 can selectively control the differentsubsets of the TECs 120, the controller 106 has substantial flexibilityin how the temperature of the cooling chamber 102 is increased. Aftercontrolling the TECs 120 to increase the temperature of the coolingchamber 102, the process returns to step 1100 and is repeated.

Returning to step 1102, if the temperature of the cooling chamber 102 isgreater than the upper threshold of the steady state range, thecontroller 106 then determines whether the temperature of the coolingchamber 102 is greater than a predetermined maximum allowabletemperature for the cooling chamber 102 (step 1108). If so, the processproceeds to step 1112. If not, the controller 106 controls the TECs 120to decrease the temperature of the cooling chamber 102 (step 1110). Thecontroller 106 controls the TECs 120 to decrease the temperature of thecooling chamber 102 by activating one or more previously deactivatedTECs 120, increasing the current input to one or more of the activatedTECs 120 from I_(COPmax) to a value that is greater than I_(COPmax)(e.g., I_(max)), and/or increasing the duty cycle of one or more of theactivated TECs 120. Using the TECs 120 in the embodiment of thecartridge 112 of FIG. 3 as an example, the controller 106 independentlycontrols the different subsets of the TECs 120. So, for example, ifprior to step 1110 the first subset of the TECs (i.e., the TECs 120 aand 120 b) are activated and operating at Q_(COPmax) but the remainingTECs 120 are deactivated, the controller 106 can decrease thetemperature of the cooling chamber 102 by increasing the current inputto the first subset of the TECs 120 from I_(COPmax) to a value greaterthan I_(COPmax) (e.g., I_(max)), increasing a duty cycle of the firstsubset of the TECs 120, activating the second subset of the TECs 120 tooperate at Q_(COPmax) or a capacity greater than Q_(COPmax) with adesired duty cycle (e.g., always on), activating the third subset of theTECs 120 to operate at Q_(COPmax) or a capacity greater than Q_(COPmax)with a desired duty cycle (e.g., always on), and/or activating thefourth subset of the TECs 120 to operate at Q_(COPmax) or a capacitygreater than Q_(COPmax) with a desired duty cycle (e.g., always on).

Next, whether proceeding from the “yes” branch of step 1108 or step1110, the controller 106 determines whether the temperature at thereject side of the heat exchanger 104 is greater than the predeterminedmaximum allowable temperature for the reject side of the heat exchanger104 (step 1112). If so, the controller 106 controls the TECs 120 tolower the temperature of the heat exchanger components (step 1114).Specifically, the controller 106 controls the TECs 120 to lower thetemperature of the components of the heat exchanger 104 at the rejectside (e.g., the hot side heat sink 108). Lowering the temperature of thecomponents of the heat exchanger 104 may be accomplished by deactivatingsome or all of the TECs 120, reducing the current provided to some orall of the TECs 120, or a combination thereof. The process then returnsto step 1100 and is repeated.

However, if the temperature at the reject side of the heat exchanger 104is not greater than the predetermined maximum allowable temperature, thecontroller 106 controls the TECs to decrease the temperature of thecooling chamber 102 (step 1116). As discussed above, the controller 106controls the TECs 120 to decrease the temperature of the cooling chamber102 by activating one or more previously deactivated TECs 120,increasing the current input to one or more of the activated TECs 120from I_(COPmax) to a value that is greater than I_(COPmax) (e.g.,I_(max)), and/or increasing the duty cycle of one or more of theactivated TECs 120. For example, if prior to step 1116 the first subsetof the TECs (i.e., the TECs 120 a and 120 b) are activated and operatingat Q_(COPmax) but the remaining TECs 120 are deactivated, the controller106 can decrease the temperature of the cooling chamber 102 byincreasing the current input to the first subset of the TECs 120 fromI_(COPmax) to a value greater than I_(COPmax) (e.g., I_(max)),increasing a duty cycle of the first subset of the TECs 120, activatingthe second subset of the TECs 120 to operate at Q_(COPmax) or a capacitygreater than Q_(COPmax) with a desired duty cycle (e.g., always on),activating the third subset of the TECs 120 to operate at Q_(COPmax) ora capacity greater than Q_(COPmax) with a desired duty cycle (e.g.,always on), and/or activating the fourth subset of the TECs 120 tooperate at Q_(COPmax) or a capacity greater than Q_(COPmax) with adesired duty cycle (e.g., always on). After decreasing the temperatureof the cooling chamber 102 in step 1116, the process returns to step1100 and is repeated.

As an example, assume that the temperature data indicates that thecooling chamber 102 is at 0.9° C. and the reject side of the heatexchanger 104 is at 19° C. In addition, for this example, the set pointtemperature for the cooling chamber 102 is 2.2° C., the upper thresholdof the steady state range is 5.0° C., the lower threshold of the steadystate range is 1.0° C., the maximum allowable temperature in the coolingchamber 102 is 15° C., and the maximum allowable temperature at thereject side of the heat exchanger 104 is 20° C. Using this example, thecontroller 106 first determines that the temperature of the coolingchamber 102 (0.9° C.) does not exceed the upper threshold value of thesteady state range (5.0° C.). Thus, the controller 106 performs step1104 where the controller 106 determines that the temperature of thecooling chamber 102 (0.9° C.) is less than the lower threshold of thesteady state range (1.0° C.). Therefore, the controller 106 performsstep 1106 to increase the temperature of the cooling chamber 102. Afterperforming step 1106, the controller 106 returns to step 1100 to therebyreceive updated temperature data and continue the process.

As another example, assume that the temperature data indicates that thetemperature of the cooling chamber 102 is 14° C. and the temperature atthe reject side of the heat exchanger 104 is 18° C. In addition, forthis example, the set point temperature for the cooling chamber 102 is2.2° C., the upper threshold of the steady state range is 5.0° C., thelower threshold of the steady state range is 1.0° C., the maximumallowable temperature in the cooling chamber 102 is 15° C., and themaximum allowable temperature at the reject side of the heat exchanger104 is 20° C. Using this example, the controller 106 determines that thetemperature of the cooling chamber 102 (14° C.) is greater than theupper threshold of the steady state range (5.0° C.). Therefore, thecontroller 106 performs step 1108, where the controller 106 determinesthat the temperature of the cooling chamber 102 (14° C.) is less thanthe maximum allowable temperature of the cooling chamber 102 (15° C.).Accordingly, the controller 106 performs step 1110 to thereby decreasethe temperature of the cooling chamber 102.

In a third example, the temperature data indicates that the temperatureof the cooling chamber 102 is 17° C. and the temperature of the heatexchanger 104 is 22° C. In addition, for this example, the set pointtemperature for the cooling chamber 102 is 2.2° C., the upper thresholdof the steady state range is 5.0° C., the lower threshold of the steadystate range is 1.0° C., the maximum allowable temperature in the coolingchamber 102 is 15° C., and the maximum allowable temperature at thereject side of the heat exchanger 104 is 20° C. In step 1102, thecontroller 106 determines that the temperature of the cooling chamber102 is greater than the upper threshold of the steady state range.Therefore, the controller 106 performs step 1108, where the controller106 determines that the temperature of the cooling chamber 102 (17° C.)exceeds the maximum allowable temperature within the cooling chamber 102(15° C.). Accordingly, the controller 106 performs step 1112, where thecontroller 106 determines whether the temperature at the reject side ofthe heat exchanger 104 exceeds the maximum allowable temperature at thereject side of the heat exchanger 104. In accordance with an embodimentof the present disclosure, the maximum allowable temperature at thereject side of the heat exchanger 104 is a temperature beyond whichcomponents of the heat exchanger 104 may overheat and become damaged. Anexample of when the temperature at the reject side of the heat exchanger104 exceeds the maximum allowable temperature at the reject side of theheat exchanger 104 is when there is great amount of heat leak throughthe cooling chamber 102, such as when a door of the cooling chamber 102is left open. In the scenario where the door of the cooling chamber 102is left open, the thermoelectric refrigeration system 100 is trying topull down the temperature of the cooling chamber 102 to the set pointtemperature. Here, as there is a great amount of heat leak, thecomponents of the heat exchanger 104 may not be able to pull down thetemperature of the cooling chamber 102 and instead become overworked,thereby overheating (i.e., exceeding the maximum allowable temperatureat the reject side of the heat exchanger 104). Another example of whenthe temperature at the reject side of the heat exchanger 104 exceeds themaximum allowable temperature at the reject side of the heat exchanger104 is when proper heat transfer is not occurring between the acceptloop 114 and the cooling chamber 102, such as if there is a clog in theaccept loop 114, if there is an issue with the cooling medium within theaccept loop 114, or the like. In the third example, the temperature atthe reject side of the heat exchanger 104 (22° C.) exceeds the maximumallowable temperature at the reject side of the heat exchanger 104 (20°C.). Accordingly, the controller 106 performs step 1114, where thecontroller 106 cools the temperature of the components of the heatexchanger 104.

FIG. 19 is a flow chart that illustrates a method of operation of thecontroller 106 to monitor the temperature at the reject side of heatexchanger 104 in accordance with one embodiment of the presentdisclosure. Initially, the controller 106 receives temperature data(step 1200). In one embodiment, the temperature data corresponds to thetemperature at the reject side of the heat exchanger 104. Afterreceiving the temperature data, the controller 106 determines whetherthe temperature at the reject side of the heat exchanger 104 exceeds themaximum allowable temperature at the reject side of the heat exchanger104, as described above with reference to step 1112 of FIG. 18 (step1202). If the temperature at the reject side of the heat exchanger 104does not exceed the maximum allowable temperature, the process returnsto step 1200 and is repeated. However, if the temperature at the rejectside of the heat exchanger 104 exceeds the maximum allowable temperatureat the reject side of the heat exchanger 104, the controller 106controls the TECs 120 to thereby reduce the temperature at the rejectside of the heat exchanger 104 (step 1204).

Multi Parallel Heat Exchange Systems

In the embodiments described above, the thermoelectric refrigerationsystem 100 includes a single heat exchange system (i.e., a single heatexchanger 104, a single accept loop 114, and a single reject loop 116).FIGS. 20A through 20C illustrate another embodiment of thethermoelectric refrigeration system 100 that includes two parallel heatexchange systems. Note that while two parallel heat exchange systems areillustrated in the embodiment of FIGS. 20A through 20C, any number oftwo or more parallel heat exchange systems may be used. As illustratedin FIG. 20A, the two parallel heat exchange systems are the same as theheat exchange system of FIG. 1. In particular, the first heat exchangesystem includes a heat exchanger 104 a that includes a hot side heatsink 108 a, a cold side heat sink 110 a, a cartridge 112 a disposedbetween the hot side and cold side heat sinks 108 a and 110 a, an acceptloop 114 a coupled to the cold side heat sink 110 a, and a reject loop116 a coupled to the hot side heat sink 108 a. The cartridge 112 aincludes one or more TECs and preferably multiple TECs that areselectively controlled by the controller 106. In some preferredembodiments, the TECs are disposed on an interconnect board that enablesselective and independent control of one or more, and preferably two ormore, subsets of the TECs in the manner described above with respect tothe cartridge 112 of FIG. 1. Likewise, the second heat exchange systemincludes a heat exchanger 104 b that includes a hot side heat sink 108b, a cold side heat sink 110 b, a cartridge 112 b disposed between thehot side and cold side heat sinks 108 b and 110 b, an accept loop 114 bcoupled to the cold side heat sink 110 b, and a reject loop 116 bcoupled to the hot side heat sink 108 b. The cartridge 112 b includesone or more TECs and preferably multiple TECs that are selectivelycontrolled by the controller 106. In some preferred embodiments, theTECs are disposed on an interconnect board that enables selective andindependent control of one or more, and preferably two or more, subsetsof the TECs in the manner described above with respect to the cartridge112 of FIG. 1. The operation of the two parallel heat exchange systemsof FIG. 20A and the control of the TECs in the cartridges 112 a and 112b is the same as that described above with respect to the correspondingheat exchange system and the cartridge 112 of FIG. 1. As such, thedetails are not repeated.

The parallel heat exchange systems provide an additional degree offreedom for the controller 106 when controlling the TECs in thecartridges 112 a and 112 b. More specifically, in addition toselectively and independently controlling one or more, and preferablytwo or more, subsets of TECs in the cartridge 112 a, the controller 106is also enabled to selectively and independently control one or more,and preferably two or more, subsets of TECs in the cartridge 112 bindependently from the subset(s) of TECs in the cartridge 112 a. As oneexample, during steady state operation, the controller 106 may activatesome or potentially all of the TECs in the cartridge 112 a preferably ator near (e.g., slightly above or potentially below) Q_(COPmax) anddeactivate all of the TECs in the cartridge 112 b, as illustrated inFIG. 20B. Conversely, during pull down or recovery, the controller 106may activate any previously deactivated TECs in the cartridge 112 a andactivate some or potentially all of the TECs in the cartridge 112 b, asillustrated in FIG. 20C. During pull down or recovery, the activatedTECs are preferably operated at Q_(COPmax), Q_(max), or some valuebetween Q_(COPmax) and Q_(max).

One non-limiting advantage of the parallel heat exchangers 104 a and 104b is the ability to completely isolate large numbers of TEC subsetswhile at the same time providing for large recovery capacity withoutsuffering from parasitic losses associated with deactivated TECs locatedin the same heat exchanger 104 a, 104 b as the active TECs. Anothernon-limiting advantage of the parallel heat exchangers 104 a and 104 bis related to maximizing efficiency by better balancing of the differentcontrol regimes to the relevant heat exchanger volume/dissipation area.

Cascaded Heat Sinks

In a further embodiment of the present disclosure, arrays of TECs may becascaded in order to maintain different cooling chambers at differentset point temperatures. In one embodiment, a single thermoelectricrefrigeration system may have a first cooling chamber and a secondcooling chamber each having different set point temperatures. In oneembodiment, a first set of TECs (e.g., TECs in a first cartridge)provide cooling for the first cooling chamber. In addition, a second setof TECs (e.g., TECs in a second cartridge) provide cooling for thesecond cooling chamber, where the set point temperature of the secondcooling chamber is lower than that of the first cooling chamber. In thisembodiment, the first and second sets of the TECs are thermally coupledto one another via cascaded heat sinks. In this embodiment, duringcooling of the first cooling chamber, the first set of TECs extract heatfrom the first cooling chamber and operate to reject the extracted heatto an environment external to the first cooling chamber. In thisembodiment, during cooling of the second cooling chamber, the second setof TECs extract heat from the second cooling chamber and then operate toreject the extracted heat to the first set of TECs. Here, the first setof TECs operates to reject the heat extracted from the second coolingchamber to an environment external to the first and second coolingchambers. In this embodiment, the first set of TECs may operateindependently of the second set of TECs. In particular, the first setpoint temperature may be different from the second set pointtemperature. Further, there may be different modes of operation for eachof the cooling chambers (e.g., the first cooling chamber may be in pulldown while the second cooling chamber is in steady state due to openingof a door of the first cooling chamber).

In this regard, FIG. 21 illustrates a thermoelectric refrigerationsystem 184 having cooling chambers 186 and 188 in accordance with anembodiment of the present disclosure. In this embodiment, the coolingchambers 186 and 188 have different set point temperatures. For example,if the thermoelectric refrigeration system 184 is a householdrefrigerator, the cooling chamber 186 may correspond to a freezer andthe cooling chamber 188 may correspond to a refrigerator. Thethermoelectric refrigeration system 184 also includes a heat exchanger190 in accordance with another embodiment of the present disclosure.Here, the heat exchanger 190 includes a hot side heat sink 192 and twocold side heat sinks, namely, a cold side heat sink 194 and a cold sideheat sink 196. The hot side heat sink 192 thermally couples with areject loop 198 and operates to reject heat from the cooling chambers186 and 188 in a manner similar to that described above with respect tothe cooling chamber 102, the hot side heat sink 108, and the reject loop116 of FIG. 1. In this example, the heat exchanger 190 is between aninterior wall 200 that defines the cooling chamber 188 and an outer wall202 of the thermoelectric refrigeration system 184.

The heat exchanger 190 also includes cartridges 204 and 206. Thecartridge 204 thermally couples with both the cold side heat sink 194and the cold side heat sink 196. The cartridge 204 includes TECs asdescribed above with reference to the cartridge 112 of FIG. 1 where acold side of the TECs is thermally coupled to the cold side heat sink194 and a hot side of the TECs is thermally coupled to the cold sideheat sink 196. Moreover, the TECs disposed within the cartridge 204 mayhave any number of TECs, as described above with reference to FIGS. 3through 8. The TECs within the cartridge 204 facilitate the transfer ofheat between the cold side heat sink 194 and the cold side heat sink196. The heat that is transferred between the cold side heat sink 194and the cold side heat sink 196 is heat extracted from the coolingchamber 186 via an accept loop 208.

The cartridge 206 is disposed between the hot side heat sink 192 and thecold side heat sink 196. The cartridge 206 includes TECs as describedabove with reference to the cartridge 112 of FIG. 1 where a cold side ofthe TECs is thermally coupled to the cold side heat sink 196 and a hotside of the TECs is thermally coupled to the hot side heat sink 192. TheTECs in the cartridge 206 facilitate heat transfer between the cold sideheat sink 196 and the hot side heat sink 192. Moreover, the TECsdisposed within the cartridge 206 may have any number of TECs, asdescribed above with reference to FIGS. 3 through 8. In this embodiment,the heat transferred between the cold side heat sink 196 and hot sideheat sink 192 is heat extracted from the cooling chamber 188 via anaccept loop 210 and, if TECs in the cartridge 204 are activated, heatextracted from the cooling chamber 186 via the accept loop 208.

Each of the accept loops 208 and 210 operate in a manner similar to thatdescribed above with reference to the accept loop 114 of FIG. 1. Inparticular, as described above with reference to the accept loop 114,each of the accept loops 208 and 210 facilitate the extraction of heatfrom a cooled chamber (i.e., the cooling chambers 186 or 188,respectively). The TECs in the cartridges 204 and 206 are separatelycontrollable. Thus, in other words, subsets of the TECs in each of thecartridges 204 and 206 are separately controllable to maintain the setpoint temperatures in the cooling chambers 186 and 188.

As noted above, each of the cartridges 204 and 206 includes TECs havingthe functionality described above. In one embodiment of the presentdisclosure, the cartridge 206 has a greater number of TECs than thecartridge 204 such that the cartridge 206 may facilitate transferringheat from both of the accept loops 208 and 210. For example, if one ormore subsets of the TECs in the cartridge 204 are activated, then theTECs in the cartridge 206 must be controlled to have sufficient capacityto transfer the heat extracted by the accept loop 208 as well as anyheat extracted by the accept loop 210. For example, if four TECs in thecartridge 204 are operating at Q_(COPmax), then more than four TECs inthe cartridge 206 should also be operating at Q_(COPmax) in order toprovide sufficient capacity to transfer the heat transferred by theactivated TECs in the cartridge 204. In addition, if heat is also to beextracted by the accept loop 210, the TECs in the cartridge 206 arefurther controlled to provide additional capacity to extract the desiredamount of heat via the accept loop 210.

During operation of the thermoelectric refrigeration system 184, acontroller 212 controls the TECs disposed within the cartridges 204 and206 to maintain the desired set point temperatures in the coolingchambers 186 and 188. In particular, in order to maintain the desiredset point temperature within the cooling chamber 186, the controller 212controls the TECs disposed within the cartridges 204 and 206 based onthe temperature within the cooling chamber 186 and, in some embodiments,the temperature at the reject side of the heat exchanger 190 asdescribed above with respect to FIGS. 15 through 19. Therefore, in oneembodiment, the controller 212 receives temperature data relating toboth the cooling chamber 186 and the reject side of the heat exchanger190 and selectively controls the TECs disposed within the cartridges 204and 206 to maintain the desired set point temperature for the coolingchamber 186. In general, the controller 212 detects the mode ofoperation (i.e., steady state, recovery, pull down, etc.) and thenactivates/deactivates the TECs in the cartridges 204 and 206, increasesor decreases duty cycles of the TECs in the cartridges 204 and 206,and/or increases or decreases currents provided to the TECs in thecartridges 204 and 206 according to the mode of operation.

For example, if the cooling chamber 186 is at the set point temperature,the controller 212 controls the TECs within the cartridge 204 such thata predetermined number of the TECs needed for steady state operation forthe cooling chamber 186 operate at Q_(COPmax). In this example, thecartridge 204 has four TECs and three of the four TECs are operating atQ_(COPmax). In addition, during steady state operation for the coolingchamber 186, the controller 212 controls three or more of the TECswithin the cartridge 206 such that the active TECs within the cartridge206 operate at Q_(COPmax) in conjunction with and in support of thethree TECs in the cartridge 204 that operate at Q_(COPmax). In thisexample, if the controller 212 subsequently detects that the coolingchamber 186 is in recovery, the controller 212 selectively controls theTECs within the cartridge 204 in order to pull the temperature of thecooling chamber 186 down to the set point temperature. For example, thecontroller 212 may activate all four TECs in the cartridge 204 such thatall the TECs in the cartridge 204 operate at Q_(max). Moreover, when thecontroller 212 activates all four TECs in the cartridge 204 at Q_(max),the controller 212 also activates more TECs in the cartridge 206 tosupport the additional capacity provided by the newly activated TECs inthe cartridge 204.

As noted above, the thermoelectric refrigeration system 184 alsoincludes the cooling chamber 188 where the accept loop 210 facilitatesthe extraction of heat from the cooling chamber 188, as described abovewith reference to the accept loop 114 of FIG. 1. The accept loop 210thermally couples with the cold side heat sink 196 such that the coldside heat sink 196 transfers heat extracted from the cooling chamber 188to the reject loop 198 via the cartridge 206 and the TECs disposedtherein. Thus, the reject loop 198 operates to reject heat extractedfrom the cooling chamber 186 and the cooling chamber 188. As notedabove, the cartridge 206 includes TECs that work in conjunction with theTECs disposed within the cartridge 204. Here, the cartridge 206 includesadditional TECs that facilitate the transfer of heat extracted from thecooling chamber 188 to the hot side heat sink 192.

In addition to controlling the TECs disposed within the cartridge 206 tosupport heat transfer by the activated TECs disposed within thecartridge 204, the controller 212 selectively controls the TECs disposedwithin the cartridge 206 to maintain the desired set point temperaturewithin the cooling chamber 188 in accordance with the methods of FIGS.15 through 19 described above. Thus, the controller 212 receivestemperature data for the cooling chamber 188 and selectively controlsthe TECs disposed within the cartridge 206 accordingly. For example,during steady state operation, the controller 212 selects TECs withinthe cartridge 206 that are not facilitating heat transfer associatedwith the cooling chamber 186 such that the selected TECs operate atQ_(COPmax). Continuing this example, when the controller 212 detectsthat the cooling chamber 188 is in recovery, in one embodiment, thecontroller 212 controls the selected TECs such that the selected TECsoperate at Q_(max). In addition, the controller 212 may selectadditional TECs that are not activated such that these additional TECsoperate at Q_(max) or at some point between Q_(COPmax) and Q_(max). Inthis scenario, if the cartridge 206 includes ten TECs and four of theTECs facilitate heat transfer associated with the cooling chamber 186,during steady state operation of the cooling chamber 188, of the sixremaining TECs, the controller 212 may select three of the remainingTECs to operate at Q_(COPmax). However, when the cooling chamber 188 isin recovery and the controller 212 needs to pull the temperature of thecooling chamber 188 down to the set point temperature, the controller212 may control the three TECs operating at Q_(COPmax) such that theseTECs operate at Q_(max) and then, of the three remaining TECs that arenot activated, the controller 212 may activate one or more additionalTECs to also operate at Q_(max).

In the above scenario, of the activated TECs in the cartridge 206, fourwere operating at Q_(COPmax) in order to facilitate the transfer of heatfrom the cooling chamber 186. It should be noted that in the scenarioabove when the cooling chamber 188 was in recovery, in accordance withembodiments of the present disclosure, the controller 212 may havecontrolled the four TECs that were assisting with the heat transfer ofthe heat extracted from the cooling chamber 186 such that these fourTECs operated at Q_(max). Here, the four TECs would still work tomaintain the cooling chamber 186 at the set point temperature (since theTECs need only operate at Q_(COPmax)) while at the same time assistingwith pulling down the temperature of the cooling chamber 188 to the setpoint temperature (the additional heat that may be extracted between thepoint associated with Q_(COPmax) and Q_(max) as shown with reference toFIG. 2). It should be noted that all the TECs in the cartridge 206 maybe controlled to operate at Q_(max) when the cooling chamber 186 and thecooling chamber 188 are in recovery.

Thermal Diode Effect and Thermal Isolation of Heat Exchange System

In some preferred embodiments of the present disclosure, the heatexchange system(s) disclosed herein also provide a thermal diode effectand thermal isolation of the heat exchanger from the cooling chamber(s)and the external environment. This is beneficial because the thermaldiode effect and the thermal isolation of the heat exchanger(s) prevent,or at least minimize, heat leak back from the external environment,through the heat exchanger(s), to the cooling chamber(s). In thisregard, FIG. 22 illustrates one embodiment of the heat exchanger 104 ofFIG. 1 wherein the heat exchanger 104 is thermally isolated from thecooling chamber 102 and the outer wall 118 of the thermoelectricrefrigeration system 100 such that heat leak back from the heatexchanger 104 to the cooling chamber 102 does not occur when the heatexchanger 104 is not actively facilitating the extraction of heat fromthe cooling chamber 102 (i.e., when all of the TECs are inactive).

As noted above with respect to FIG. 1, the heat exchanger 104 includesthe cold side heat sink 110 and the hot side heat sink 108 where thecartridge 112 is disposed between the cold side heat sink 110 and thehot side heat sink 108. As illustrated in FIG. 22, in order to providethermal isolation of the heat exchanger 104, the heat exchanger 104 isphysically separated from, and physically attached to, the interior wall115 via standoffs 220. In particular, the standoffs 220 couple with thecold side heat sink 110 and the interior wall 115 such that thestandoffs 220 physically and thermally isolate the heat exchanger 104from the interior wall 115 while at the same time mount the heatexchanger 104 within the thermoelectric refrigeration system 100. Inaccordance with one embodiment of the present disclosure, the standoffs220 may be formed from any type of material that minimizes thermalconductance, such as any low thermal conductivity material, includingceramic, plastic, or the like. Moreover, as may be seen with respect toFIG. 22, the heat exchanger 104 is disposed between the interior wall115 and the outer wall 118 (and thus the cooling chamber 102), where theheat exchanger 104 is also thermally isolated from the interior wall 115and the outer wall 118 by insulation 222.

When the thermal isolation of the heat exchanger 104 is combined with athermal diode effect provided by the accept and reject loops 114 and116, heat leak back from the external environment and the heat exchanger104 into the cooling chamber 102 when the TECs disposed within thecartridge 112 are all deactivated or are in an “off” state during dutycycle control. In one embodiment, the accept and reject loops 114 and116 operate according to thermosiphon principles (i.e., arethermosiphons) and, as such, provide a thermal diode effect. Thisthermal diode effect is illustrated with respect to FIGS. 23 and 24.FIG. 23 illustrates heat transfer through the heat exchange system whenone or more TECs in the heat exchanger 104 are activated or in the “on”state during duty cycle control. As illustrated, when one or more of theTECs are on, the cooling medium in the accept loop 114 is condensed bythe cold side heat sink 110 of the heat exchanger 104 such that thecondensed cooling medium flows through the accept loop 114 via gravityforces. When flowing through the accept loop 114, the cooling mediumextracts heat from the cooling chamber 102. The extracted heatevaporates the cooling medium. The evaporated cooling medium thenreturns to the cold side heat sink 110 of the heat exchanger 104 viabuoyancy forces. This process continues to facilitate heat extractionfrom the cooling chamber 102. Conversely, at the reject side, the heatexchange medium in the reject loop 116 is evaporated by the hot sideheat sink 108 of the heat exchanger 104. The evaporated heat exchangemedium flows through the reject loop 116 via buoyancy forces such thatheat is rejected to the external environment. Due to the heat rejection,the heat exchange medium is condensed, and the condensed heat exchangemedium returns to the hot side heat sink 108 via gravity. The processcontinues to provide heat rejection to the external environment.

Once the TECs in the heat exchanger 104 are all deactivated or in the“off” state during duty cycle control, the accept and reject loops 114and 116 prevent the transfer of heat through the accept and reject loops114 and 116 toward the cooling chamber 102 as illustrated in FIG. 24.More specifically, when all of the TECs are deactivated or in the “off”state during duty cycle control, the cold side heat sink 110 of the heatexchanger 104 is no longer sufficiently cold to condense the coolingmedium in the accept loop 114. As such, the cooling medium in the acceptloop 114 evaporates and collects at the cold side heat sink 110, therebypreventing further heat transfer through the accept loop 114. Therefore,it can be seen that the accept loop 114 provides heat transfer away fromthe cooling chamber 102 (i.e., heat extraction) but prevents heattransfer toward the cooling chamber 102 (i.e., heat leak back into thecooling chamber 102). In this manner, the accept loop 114 provides athermal diode effect. In a similar manner, the hot side heat sink 108 isno longer sufficiently hot to evaporate the heat exchange medium in thereject loop 116. As such, the heat exchange medium in the reject loop116 condenses and collects at the hot side heat sink 108, therebypreventing further heat transfer through the reject loop 116. Therefore,it can be seen that the reject loop 116 provides heat transfer away fromthe heat exchanger 104 (i.e., heat rejection) but prevents heat transfertoward the heat exchanger 104 (i.e., heat leak back from the externalenvironment to the heat exchanger 104). In this manner, the reject loop116 provides a thermal diode effect. Importantly, the thermal insulationof the heat exchanger 104 and the thermal diode effect of the accept andreject loops 114 and 116 enable: (1) deactivation of all of the TECs inthe heat exchanger 104 with no or minimal heat leak back into thecooling chamber 102 and (2) duty cycle control of the TECs in the heatexchanger 104 with no or minimal heat leak back into the cooling chamber102.

Notably, while the heat exchange system of FIG. 1 includes both theaccept and reject loops 114 and 116, the present disclosure is notlimited thereto. The heat exchange system may alternatively be a hybridsystem that includes the accept loop 114 on the accept side of the heatexchanger 104 and an alternative heat exchange mechanism (e.g., fins anda fan) on the reject side of the heat exchanger 104. In this alternativeembodiment, the accept loop 114 still provides a thermal diode effectthat prevents heat leak back into the cooling chamber 102 when all ofthe TECs in the heat exchanger 104 are deactivated or in the “off” stateduring duty cycle control, as illustrated in FIG. 25. As anotheralternative, the heat exchange system may be a hybrid system thatincludes the reject loop 116 on the reject side of the heat exchanger104 and an alternative heat exchange mechanism (e.g., fins and a fan) onthe accept side of the heat exchanger 104. In this alternativeembodiment, the reject loop 116 provides a thermal diode effect thatprevents heat leak back from the external environment to the heatexchanger 104.

FIG. 26 illustrates thermal isolation of the heat exchanger 190 of FIG.21 in accordance with one embodiment of the present disclosure. Here,the heat exchanger 190 interfaces with the interior wall 200 thatdefines the cooling chamber 188 via the standoffs 220. In particular,the standoffs 220 couple with the cold side heat sink 194 and theinterior wall 200 such that the standoffs 220 physically and thermallyisolate the heat exchanger 190 from the cooling chamber 188 while at thesame time mount the heat exchanger 190 within the thermoelectricrefrigeration system 184. The insulation 222 around the heat exchanger190 thermally isolates the heat exchanger 190 from the cooling chamber188 and the outer wall 202. Further, in a manner similar to thatdescribed above, the reject loop 198 and the accept loops 208 and 210each provide a thermal diode effect. Notably, in this embodiment, thereare two accept loops, namely the accept loops 208 and 210, that eachprovide a thermal diode effect that prevents heat leak back into thecorresponding cooling chambers 186 and 188. Accordingly, when the heatexchanger 190 is not actively extracting heat from the cooling chamber186 or 188, heat leak back into the cooling chambers 186 and 188 doesnot occur via the heat exchanger 190.

Heat Sink Configuration

As noted above with respect to FIG. 1, the accept loop 114 transfersheat extracted from the cooling chamber 102 to the cold side heat sink110 and the hot side heat sink 108 transfers the extracted heat to thereject loop 116. FIG. 27 is a schematic illustrating a configuration ofthe cold side heat sink 110 in accordance with one embodiment of thepresent disclosure. It should be noted that while this discussionfocuses on the cold side heat sink 110, this discussion is equallyapplicable to the cold side heat sinks 194 and 196 and the hot side heatsinks 108 and 192. The cold side heat sink 110 includes two inlet/outletports 226/228 through which the cooling medium enters and exits the coldside heat sink 110 after heat transfer with the cooling chamber 102and/or one of the activated TECs of the array of TECs 120 in thecartridge 112. Specifically, when the cooling medium enters theinlet/outlet ports 226/228, the cooling medium includes heat extractedfrom the cooling chamber 102. Heat extracted from the cooling chamber102 is transferred to the cooling medium via thermal convection,conduction, and radiation and then to the cold side heat sink 110 viathermal convection, conduction, and radiation between the cooling mediumand the cold side heat sink 110. The extracted heat is then transferredto the array of TECs 120 via fins 230 disposed on the cold side heatsink 110 to a plate 232 as shown with respect to FIG. 28, which isthermally coupled to the array of TECs 120.

As shown with reference to FIG. 27, each of the fins 230 has anelongated shape and respectively spans a length L₁ through L₄. Moreover,as may be seen with respect to FIG. 28, the fins 230 extend a height hand are spaced apart from each other a width w. Thus, each of the fins230 has an effective surface area for transferring heat that is afunction of the length L₁ through L₄ and the height h. It should benoted that while the cold side heat sink 110 is described as having thefins 230 having the configuration and dimensions noted above, the coldside heat sink 110 may have fins of any configuration and may have anydimensions dependent on heat loads and space constraints. In someembodiments, the configuration and dimensions of the fins 230 may be afunction of the type of cooling medium used in the accept loop 114 and atemperature differential between the cooling chamber 102, the heatexchanger 104, and an ambient temperature. Moreover, the dimensions andconfiguration of the fins 230 may also be a function of the fluidpressures within the accept loop 114 and the reject loop 116 and anyheat leak within the thermoelectric refrigeration system 100.

FIG. 29 illustrates another embodiment of the cold side heat sink 110that includes a heat sink 234. In one embodiment, the thermoelectricrefrigeration system 100 does not include the reject loop 116 butinstead the heat sink 234 where the thermoelectric refrigeration system100 includes a fan (not shown) that evacuates the heat absorbed by theheat sink 234 to an environment external to the thermoelectricrefrigeration system 100. Moreover, in a further embodiment of thepresent disclosure, the thermoelectric refrigeration system 100 mayinclude both the heat sink 234 and the reject loop 116, thereby forminga hybrid configuration where both the heat sink 234 and the reject loop116 operate to reject heat extracted from the cooling chamber 102 to anenvironment external to the thermoelectric refrigeration system 100.

Divorced Heat Exchanger

Some embodiments of the present disclosure maximize, or at leastincrease, the heat extraction capabilities of a thermoelectricrefrigeration system by increasing the available surface area of aninterior wall of the cooling chamber and/or the available surface areaof an outer wall that is usable for heat transfer via the accept andreject loops, respectively. In general, these embodiments provide a heatexchanger having physically separated, or divorced, hot side and coldside heat sinks that are thermally coupled by a heat conduit. In oneembodiment, the cartridge containing the TECs is physically attached tothe cold side heat sink, where the heat conduit thermally couples a hotside of the TECs to the hot side heat sink. In another embodiment, thecartridge containing the TECs is physically attached to the hot sideheat sink, where the heat conduit thermally couples the cold side of theTECs to the cold side heat sink.

In this regard, FIG. 30 illustrates one embodiment of a heat exchangerthat includes a heat conduit 236 that enables physical separation of thecold side heat sink 110 from the hot side heat sink 108. In accordancewith embodiments of the present disclosure, the heat conduit 236 may beany device suitable for conducting heat between the cold side heat sink110 and the hot side heat sink 108. Examples of devices that may be usedfor the heat conduit 236 include a traditional heat pipe, where the heatpipe allows for the passive movement of heat in a downward directionfrom the cold side heat sink 110 to the hot side heat sink 108.

In an alternative embodiment, the heat conduit 236 may comprise aconvective coupling that works in conjunction with a plenum tofacilitate heat transfer between the cold side heat sink 110 and the hotside heat sink 108. Moreover, in another embodiment, the heat conduit236 may include a fluid loop having a heat transfer fluid where a pumppumps the heat transfer fluid between the cold side heat sink 110 andthe hot side heat sink 108. In an embodiment where the heat conduit 236includes a fluid loop, the heat transfer fluid carries heat from thecold side heat sink 110 to the hot side heat sink 108. Additionally, theheat conduit 236 may transfer heat via direct conduction, where the heatconduit 236 conductively transfers heat from the cold side heat sink 110to the hot side heat sink 108.

The heat conduit 236 is physically and thermally coupled to thecartridge 112 using any well-known technique, such as a spreader plate,where the spreader plate interfaces with the TECs 120 disposed withinthe cartridge 112. As noted above, during cooling of the cooling chamber102, heat from the cooling chamber 102 thermally transfers to the acceptloop 114. The heat from the accept loop 114 is then thermallytransferred to the TECs 120 disposed within the cartridge 112, also asdescribed above. The heat is transferred from the TECs 120 to the heatconduit 236, and the heat conduit 236 transfers the heat to the hot sideheat sink 108. Moreover, the heat conduit 236 physically and thermallycouples with the hot side heat sink 108 using any well-known technique,such as a mechanical assembly 237 where the heat conduit 236 couplesdirectly to the hot side heat sink 108. Note that, in an alternativeembodiment, the heat conduit 236 is directly connected to the hot sideheat sink 108 such that the mechanical assembly 237 is not needed. Itshould be noted that while the cartridge 112 is shown being thermallycoupled to the cold side heat sink 110 such that the heat conduit 236thermally couples with the cartridge 112 and the hot side sink 108, thecartridge 112 may be thermally coupled with the hot side heat sink 108such that the heat conduit 236 may directly thermally couple with thecold side heat sink 110 and the cartridge 112 when the cartridge 112 iscoupled with the hot side heat sink 108. It should be noted that anymethodology may be used to divorce the cold side heat sink 110 from thehot side heat sink 108 where the cold side heat sink 110 and the hotside heat sink 108 are thermally coupled with each other. For example,the cold side heat sink 110 and the hot side heat sink 108 may beconductively and convectively coupled with each other. Moreover, thecold side heat sink 110 and the hot side heat sink 108 may be thermallycoupled using a pumped loop or may be radiatively coupled with eachother.

FIG. 31 is a schematic illustrating heat flow for the heat exchanger 104of FIG. 30 in accordance with one embodiment of the present disclosure.In particular, heat is extracted from the cooling chamber 102 as denotedby Q_(ACCEPTIN) and then transferred to the heat conduit 236 asindicated by Q_(ACCEPTOUT). The heat conduit 236 then transfers the heatto the reject loop 116 as denoted by Q_(REJECTIN), where the heat isultimately expelled to an environment external to the cooling chamber102, as shown by Q_(REJECTOUT).

In embodiments where the heat conduit 236 separates the cold side heatsink 110 from the hot side heat sink 108, the cold side heat sink 110 isspaced away from the hot side heat sink 108 such that, in oneembodiment, the cold side heat sink 110 is at an upper portion of thethermoelectric refrigeration system 100 and the hot side heat sink 108is at a lower portion of the thermoelectric refrigeration system 100, asshown with reference to FIGS. 32 and 33. In embodiments where the coldside heat sink 110 is disposed at an upper portion of the thermoelectricrefrigeration system 100, an accept loop 238 may envelope a greatersurface area of the cooling chamber 102 such that a greater amount ofheat transfer occurs between the cooling chamber 102 and the coolingmedium within the accept loop 238 by virtue of the greater surface areabetween the cooling chamber 102 and the accept loop 238. Morespecifically, as the accept loop 238 thermally communicates with agreater portion of the cooling chamber 102, the accept loop 238 mayfacilitate the extraction of a greater amount of heat, therebyincreasing the overall heating efficiency of a device implementing theaccept loop 238.

In addition, in embodiments where the hot side heat sink 108 is disposedat a bottom portion of the thermoelectric refrigeration system 100, areject loop 240 may extend from the bottom portion of the thermoelectricrefrigeration system 100 to the top portion of the thermoelectricrefrigeration system 100 as shown with respect to FIGS. 32 and 33 suchthat the reject loop 240 has a greater amount of surface area exposed tothe environment external to the cooling chamber 102. Here, a greateramount of heat transfer may occur between the reject loop 240 and theenvironment external to the cooling chamber 102 again, by virtue of thegreater amount of surface area between the reject loop 240 and theenvironment that is external to the cooling chamber 102. It should benoted that while FIGS. 32 and 33 illustrate the cold side heat sink 110disposed at the upper portion on the thermoelectric refrigeration system100 and the hot side heat sink 108 disposed at the bottom portion on thethermoelectric refrigeration system 100, in embodiments including theheat conduit 236, the cold side heat sink 110 may be disposed at anylocation on the thermoelectric refrigeration system 100 and the hot sideheat sink 108 may disposed at any location on the thermoelectricrefrigeration system 100, where the distance between the cold side heatsink 110 and the hot side heat sink 108 is maximized relative to thephysical dimensions of a device implementing embodiments of the presentdisclosure. With regards to the heat conduit 236, while the heat conduit236 has been shown and described with reference to the thermoelectricrefrigeration system 100, the heat conduit 236 may also be used with thethermoelectric refrigeration system 184, where the heat conduit 236thermally couples between the cold side heat sink 196 and the hot sideheat sink 192 such that the cold side heat sinks 194 and 196 aredisposed on a first side of the thermoelectric refrigeration system 184(i.e., near a top portion of the thermoelectric refrigeration system184) and the hot side heat sink 192 is disposed on a second side of thethermoelectric refrigeration system 184 (i.e., near the bottom of thethermoelectric refrigeration system 184), opposite the first side.

FIG. 34 is a block diagram of the controller 106 in accordance with oneembodiment of the present disclosure. The discussion is equallyapplicable to the controller 212. In this embodiment, the controller 106includes a hardware processor 242 and memory 244 associated with thehardware processor 242. In one embodiment, the memory 244 storesinstructions that allow the hardware processor 242 to perform theoperations noted above in accordance with the various embodiments of thepresent disclosure.

It should be noted that while the thermoelectric refrigeration systems100 and 184 have been described with reference to cooling the coolingchambers 102 and 196, the thermoelectric refrigeration systems 100 and184 may also be used for heat recovery/power generation where theoperation of the TECs 120 is reversed such that instead of taking heatfrom a cooling medium within the accept loops 114, 202, and 204, theTECs 120 are provided with heat in order to generate current through theTECs 120. More specifically, the TEC systems disclosed with reference tothe thermoelectric refrigeration systems 100 and 184 are completelyreversible thermodynamic processes as defined by the Peltier and Seebeckprocesses, such that the thermoelectric refrigeration systems 100 and184 described above may be used for heat recovery/power generationapplications. Moreover, it should be noted that while the processesdiscussed above have been described with reference to the thermoelectricrefrigeration system 100, they may also be used with the thermoelectricrefrigeration system 184. Thus, the methods detailed above with respectto FIGS. 17 through 19 may be used with the thermoelectric refrigerationsystem 184.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A thermoelectric refrigeration system comprising:at least one cooling chamber; and a thermoelectric heat exchange systemcomprising: a plurality of cascaded heat sinks comprising a plurality ofcascaded cold side heat sinks and a hot side heat sink, the plurality ofcascaded cold side heat sinks comprising: a first cold side heat sinkconnected to a first heat accept loop; and a second cold side heat sinkconnected to a second heat accept loop; a first plurality ofthermoelectric coolers located between the first cold side heat sink andthe second cold side heat sink; and a second plurality of thermoelectriccoolers located between the second cold side heat sink and the hot sideheat sink; wherein the first heat accept loop and the second heat acceptloop are not thermally in series.
 2. The thermoelectric refrigerationsystem of claim 1 wherein the at least one cooling chamber comprises afirst cooling chamber and a second cooling chamber, the first heataccept loop is in thermal contact with an interior wall of thethermoelectric refrigeration system that defines the first coolingchamber, and the second heat accept loop is in thermal contact with aninterior wall of the thermoelectric refrigeration system that definesthe second cooling chamber.
 3. The thermoelectric refrigeration systemof claim 2 further comprising a controller further configured toseparately control different subsets of the second plurality ofthermoelectric coolers located between the first cold side heat sink andthe hot side heat sink to maintain a set point in the first coolingchamber while also pumping heat rejected by the first plurality ofthermoelectric coolers of the plurality of thermoelectric coolerslocated between the first cold side heat sink and the second cold sideheat sink.
 4. The thermoelectric refrigeration system of claim 2 whereinthe first heat accept loop is integrated onto the interior wall thatdefines the first cooling chamber, and the second heat accept loop isintegrated onto the interior wall that defines the second coolingchamber.
 5. The thermoelectric refrigeration system of claim 2 whereinthe first heat accept loop is integrated into the interior wall thatdefines the first cooling chamber, and the second heat accept loop isintegrated into the interior wall that defines the second coolingchamber.
 6. The thermoelectric refrigeration system of claim 1 wherein:the first heat accept loop operates according to thermosiphon principlessuch that, when the thermoelectric heat exchange system is active, thefirst heat accept loop provides passive, two-way transport of a coolingmedium through the first heat accept loop such that heat is extractedfrom the first cooling chamber; and the second heat accept loop operatesaccording to thermosiphon principles such that, when the thermoelectricheat exchange system is active, the second heat accept loop providespassive, two-way transport of a cooling medium through the second heataccept loop such that heat is extracted from the second cooling chamber.7. The thermoelectric refrigeration system of claim 6 further comprisingthermal insulation comprising at least one of a group consisting of:thermal insulation between the plurality of cascaded heat sinks and theat least one cooling chamber and thermal insulation between theplurality of cascaded heat sinks and an external environment.
 8. Thethermoelectric refrigeration system of claim 7 wherein: the first heataccept loop operates as a thermal diode that together with the thermalinsulation operates to prevent heat leak back into the first coolingchamber when the thermoelectric heat exchange system is deactivated; andthe second heat accept loop operates as a thermal diode that togetherwith the thermal insulation operates to prevent heat leak back into thesecond cooling chamber when the thermoelectric heat exchange system isdeactivated.
 9. The thermoelectric refrigeration system of claim 6wherein the thermoelectric heat exchange system further comprises a heatreject loop that is coupled to the hot side heat sink and in thermalcontact with an exterior wall of the thermoelectric refrigerationsystem.
 10. The thermoelectric refrigeration system of claim 9 whereinthe heat reject loop operates according to thermosiphon principles suchthat, when the thermoelectric heat exchange system is active, the heatreject loop provides passive, two-way transport of a medium through thefirst heat reject loop such that heat extracted from the at least onecooling chamber is rejected to an external environment.
 11. Thethermoelectric refrigeration system of claim 10 further comprisingthermal insulation between the plurality of cascaded heat sinks and theat least one cooling chamber and thermal insulation between theplurality of cascaded heat sinks and the external environment.
 12. Thethermoelectric refrigeration system of claim 11 wherein: the first heataccept loop, the second heat accept loop, and the heat reject loopoperate as thermal diodes that together with the thermal insulationoperate to prevent heat leak back into the first and second coolingchambers when the thermoelectric heat exchange system is deactivated.13. The thermoelectric refrigeration system of claim 1 wherein: thethermoelectric heat exchange system comprises, for each cold side heatsink of the plurality of cascaded cold side heat sinks, a heat acceptloop that is coupled to the cold side heat sink and in thermal contactwith a corresponding cooling chamber of the at least one cooling chamberto thereby extract heat from the corresponding cooling chamber when thethermoelectric heat exchange system is active; and a last plurality ofthermoelectric coolers located between a last cold side heat sink of theplurality of cascaded cold side heat sinks and the hot side heat sinkhas sufficient capacity to pump the heat extracted from the at least onecooling chamber by the heat accept loops coupled to the plurality ofcascaded cold side heat sinks when the thermoelectric heat exchangesystem is active.
 14. The thermoelectric refrigeration system of claim 1wherein the at least one cooling chamber comprises a plurality ofcooling chambers, and each cold side heat sink of the plurality ofcascaded cold side heat sinks utilizes a corresponding heat exchangemechanism to extract heat from a different one of the plurality ofcooling chambers.
 15. The thermoelectric refrigeration system of claim 1wherein the thermoelectric refrigeration system further comprises acontroller configured to, for each different plurality of thermoelectriccoolers, separately control different subsets of the different pluralityof thermoelectric coolers.
 16. The thermoelectric refrigeration systemof claim 15 wherein the controller is configured to separately controlactivation and deactivation of the different subsets of the differentplurality of thermoelectric coolers.
 17. The thermoelectricrefrigeration system of claim 15 wherein the controller is configured toseparately control duty cycles of the different subsets of the differentplurality of thermoelectric coolers.
 18. The thermoelectricrefrigeration system of claim 15 wherein the controller is configured toseparately control current provided to the different subsets of thedifferent plurality of thermoelectric coolers.